In the last year, we have obtained monoclonal antibodies to the betaadrenergic receptor and have demonstrated the presence of these receptors on lymphocytes using the fluorescence-activated cell sorter. We have also obtained antisera to opiate receptors and have been unable to show their presence on lymphocytes using similar techniques. We are currently attempting to study cholinergic receptors on lymphocytes and lymphoblastoid cell lines and to make an antibody to the cholinergic receptor.